| During the last few decades,there has been an increased interest in using natural polysaccharides for immobilization of cells,proteins and probiotics.Encapsulating cells into hydrogel beads is perhaps the most significant one of all immobilization methods,of which encapsulated in alginate is the most popular.Pectin,a major component of the cell walls and soft tissues of all terrestrial plants,has the similar properties to alginate in many ways.As with alginate,ionotropic gelation of pectin can also provide mild and physiological conditions for encapsulated cells.Owing to its ability to form gels,interest in pectin has spread to applications such as cell encapsulation and tissue engineering.Compare with calcium alginate gels,calcium pectate gels are more stability and less sensitive to ions or chemical agents which destroy calcium alginate gels.Many studies demonstrated the great potential of pectin for cell immobilization or biomedical area.It is well-recognized that some characteristics of calcium pectate are influenced by its physicochemical properties.As one of the natural polysaccharides,pectin is characterized by its structural and molecular weight heterogeneity and polydispersity.Therefore,in my dissertation,for further exploration of pectins' gelation mechanism,their physicochemical properties were characterized and their preparation condition was investigated and optimized.1)Inversition of gelation mechanism of pectin and feasibiliy of application on cell immobilization.To understand the gelation mechanism of calcium pectate,quantum chemistry calculation,isothermal titration calorimetry analysis were performed.The results demonstrated that both the binding ability and the bond energy between Ca2+ and pectin were stronger than those between Ca2+and alginate.Moverover,with the decrease of DE,the bond energy between Ca2+ and pectin were increased into 2425 kJ/mol.Two kinds of commercial pectins were chosen as the experimental targets and preparated calcium pectate.As better understanding their properties,their application on encapsulating C3A cells were investigated and the resultes confirm that pectin is suitable for cell immobilization.2)Single factor model and Box-Behnken design were employed to evaluate the effect of primary innate and environmental factors on gel formation and gel properties.The result indicated DE and pectin concentration were the dominate factors.The result of models of calcium pectate conditons showed the R value was>0.9,which indicated these models could be used to describe the process under a wide range of preparation conditions.3)Moreover,since no medical grade or ultrapure pectin is commercially available,the purification process of pectin which were included filtration,gel cleaning,absorption,alcohol precipitation and desiccation was also studied and optimized.Under the purification process,the impurity elimination rate is 99.5%and yield is 43.83%± 1.53%.4)The application of optimization formula prepared by purified pectin to C3A cell culture were investigated.Briefly,the purified pecin was easier to form calcium pectate beads(under 2%,w/v).The cell viability and proliferation data indicated that C3A cells could proliferate in calcium pectate gels,which was suitable for cell culture.5)The result of EMPA indicated that the bonding site between pectin and calcium was fewer in inner of calcium pactate,which might the reason of sparse internally.Moreover,FTIR imagin indicated that the hydrogen bonds were formed between calcium pectate and cells,which were conducive to cell attachment and proliferation.Above all,the purified pectin which could be applied for cell encapsulated were prepared.The gelation mechanism of pectin were investigated and the controllable prepared of calcium pectate were also optimized.Therefore,this study may provide some useful information on the basic research and applications of pectins. |
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